346 M. Arfwcdson's Analysis of some Minerals. [May, 



In a set of experiments which Prof. Berzelius made upon 

 almost all minerals by means of the blowpipe, he expressed his 

 opinion respecting this mineral that it did not contain lime as 

 an essential constituent, but that in all probability chrysoberyl is 

 a pure subsilicate of alumina. 



I have found this opinion confirmed by the following analytical 

 experiments. On that account they may deserve to be stated in 

 this place. 



Analysis. 



0614 gramme of the mineral were reduced to a fine powder 

 in the agate mortar, and afterwards separated from all the 

 coarser particles by washing. This powder was mixed with a' 

 sufficient quantity of caustic potash, and raised to a red heat in 

 a silver crucible. After the heat had been kept up a full hour, 

 the mass was found in a state of semifusion. It was washed out 

 of the vessel with water, and treated in the usual way with 

 muriatic acid, which left undissolved 0*238 gr. This residue 

 was heated again with potash, and dissolved in muriatic acid. 

 The undissolved portion now weighed 0*137 gr. The heating 

 with potash was repeated still another time, and there now 

 remained undissolved by the muriatic acid 0*108 gr. which, on 

 examination, proved to be pure silica.* (a) 



The solutions in muriatic acid were mixed with the water 

 employed to edulcorate the silica, and the liquid was precipitated 

 by caustic ammonia added in as small excess as possible. The 

 precipitate, after being well washed, and heated to redness, 

 weighed 0*507 gr. When dissolved in sulphuric acid, it left 

 0*007 gr. (/;) of silica, and the solution gave with caustic potash 

 a precipitate, which was again redissolved by an additional dose 

 of the potash, with the exception of some flocks of peroxide of 

 iron which could not be weighed. The matter dissolved by the 

 sulphuric acid was of course alumina, and its quantity (subtract- 

 ing the silica) was 0*500 (c). 



For the greater security, the alkaline solution was saturated 

 with muriatic acid, till the precipitate was redissolved, after 

 which carbonate of ammonia was added in great excess. Had 

 any glucina or yttria existed in the matter, it would have been 

 dissolved by this excess of carbonate of ammonia, and would 

 have fallen when the filtered liquid was boiled till the excess of 

 ammonia was driven off; but the liquid stood this test without 

 any precipitate appearing. 



The liquid which had been precipitated by caustic ammonia 

 was neutralized by muriatic acid, and mixed with some drops of 

 oxalate of ammonia ; but even after the interval of 12 hours, the 

 liquid had not the least appearance of turbidness ; nor could any 



* To satisfy myself whether the silica be pure, I am in the habit of fusing it with a 

 good quantity of carbonate of potash. If the fused mass dissolve in water without resi- 

 due, 1 consider the silica as free from any admixture of foreign earth. 



